Question

Each of the three circles have a radius of 10. The line OA contains the center of the three circles, and the line OB is tangent to the right-hand circle. Find the length of segment CD

Answer 1

There are a lot of loose ends in this explanation. You give no explanation of the relative positions of the circles, where A,B,C,D are, or even O.

All you say is there are 3 circles (somewhere) and that their "center" is on line OA. (by the way, what is the "center" of 3 circles?)